Kopotun, K. A., Leviatan, D., & Shevchuk, I. A. (2010). Are the degrees of the best (co)convex and unconstrained polynomial approximations the same? II. Ukrains’kyi Matematychnyi Zhurnal, 62(3), 369–386. https://umj.imath.kiev.ua/index.php/umj/article/view/2873